Measurements versus Predictions for a Hybrid (Hydrostatic plus Hydrodynamic Thrust Bearing for a Range of Orifice Diameters

摘要

A fixed geometry hybrid thrust bearing is investigated with three different supplyorifice diameters. The test rig uses a face-to-face thrust bearing design, with the testbearing acting as the rotor loading mechanism. A hydraulic shaker applies the staticaxial load, which is reacted by a second thrust bearing. The rotor is supported radiallyby two water-lubricated fluid film journal bearings and is attached to a 30,600 rpmmotor via a high speed coupling with very low axial stiffness. Thrust bearings withthree different orifice diameters (1.63, 1.80, and 1.93 mm) are tested for a range ofsupply pressures, fluid film thicknesses, and rotational speeds. The water-lubricated testbearings have eight pockets, with feed orifices located centrally in each pocket.Experimental results are comparted to predictions found using bulk flow modelHYDROTHRUST.Analysis of the data reveals generally good agreements between predictions andmeasurements. Thrust-bearing inlet supply and inner radius flow rates all decreasedwith decreasing orifice diameters and bearing axial clearances. In most cases, thebearings with larger orifice diameters exhibit higher recess pressure ratios, operating clearances, and flow rates. The largest orifice diameter configuration does not displayhigher recess pressure ratios or operating clearances at high speeds for some supplypressures, but it does continue to require additional lubricant flow rate compared to thesmaller orifice bearings. In these cases, the results are not reflected in predictions, whichotherwise correlate very well with experimental measurements. Estimations of staticloading axial stiffness are obtained using experimental results.An optimum hybrid thrust bearing orifice diameter will depend on the conditionsof individual applications. Larger orifices generally provide larger operating clearancesand higher stiffnesses, but also require higher flow rates. For most applications, acompromise of bearing performance parameters will be desired. The test results andcomparisons presented will aid in sizing orifice diameters for future hybrid thrustbearing designs.